Benefits
Stress response in healthy adults
In 22 healthy men who took a placebo and then the strain for four weeks each, the rise in cortisol and anxiety during a cold-water stress test was smaller and daily stress ratings fell, but the order was fixed rather than randomized. In a randomized crossover study in 20 male students, stress scores rose during exams on both the strain and placebo.
Sleep quality ratings in adults with poor sleep
In 89 adults with poor sleep, the main sleep score improved on both the strain and placebo over eight weeks, but rated sleep quality and daytime sleepiness improved faster by week four; a wrist activity monitor showed no difference. Students reported better sleep quality and duration during exams than on placebo, and in a low-mood trial sleep scores were better at week four but not week eight.
Mood and vitality in adults with low mood
In 168 adults with mild to moderate depressive symptoms, the main depression score did not differ from placebo at four or eight weeks. A second mood questionnaire and mental health, vitality and social functioning ratings were better at week four, and vitality was still better at week eight. Students taking it during exams saw no change in depression scores.
Visual and spatial memory in healthy men
In the 22-man study, performance on a visual and spatial memory task improved slightly after four weeks on the strain. A later randomized crossover study in 20 male students during exams found no effect on working memory, visual memory, sustained attention or perception, so the memory finding has not been repeated.
Mechanism of action
Brain activity changes (MEG and EEG)
In 40 healthy volunteers, four weeks of the strain changed resting brain rhythms measured by magnetoencephalography, with more theta activity in frontal and cingulate areas that tracked vitality ratings, and changed brain responses during a social exclusion game, though stress ratings did not differ. The 22-man study found greater frontal midline EEG mobility. What these changes mean day to day is unclear.
Stress hormone response
Cortisol output during a cold-water stress test was lower after four weeks on the strain than after placebo in the 22-man study. This came from a single non-randomized study.
Immune signaling from the strain's sugar coat and tryptophan metabolites (lab and animal evidence)
In lab and mouse work, a sugar coat on the strain's surface (exopolysaccharide) prompted immune cells to release the anti-inflammatory signal IL-10, and the strain made indole lactic acid, which damped inflammatory signals. Blood tryptophan and kynurenic acid rose in people taking it. How this links to mood or stress is not known.
Strain-specific effects (animal evidence)
In anxious mice, B. longum 1714 and another bifidobacterium (B. breve 1205) each reduced some anxiety-like behaviors but differed on others, and neither changed the stress hormone corticosterone. This supports treating 1714 results as specific to this strain rather than to all B. longum products.
Clinical trials
Within-participant study in which everyone took placebo for 4 weeks and then 1 x 10^9 CFU a day of B. longum 1714 for 4 weeks, in fixed order. Run at University College Cork; one co-author worked for Alimentary Health (Allen et al. 2016, Transl Psychiatry).
22 healthy men.
After the strain, the cortisol and anxiety rise during a socially evaluated cold pressor test was smaller and daily reported stress fell. Visual and spatial memory improved slightly and frontal midline EEG mobility increased. Because the order was not randomized, time and practice effects cannot be ruled out.
Randomized, double-blind, placebo-controlled trial of 1 x 10^9 CFU a day for 4 weeks, with brain activity measured by magnetoencephalography during the Cyberball social exclusion game. EU-funded; Alimentary Health supplied the product and its technical director was a co-author (Wang et al. 2019, Am J Gastroenterol).
40 healthy volunteers, 20 per group.
The strain increased resting theta power in frontal and cingulate cortex, linked with vitality ratings, and changed brain responses after social stress. Both groups felt more socially stressed after the game, with no difference in behavior between groups, which the authors put down to the small sample.
Randomized, placebo-controlled crossover trial with post-intervention assessments during the exam period. Run at APC Microbiome Ireland with public research funding (Moloney et al. 2021, Brain Behav Immun Health).
20 male university students.
Stress and depression scores rose during exams on both the strain and placebo. Overall sleep quality and sleep duration were better on the strain, but working memory, visual memory, sustained attention and perception did not differ.
Randomized, double-blind, placebo-controlled trial of 1 x 10^9 CFU a day for 8 weeks. Four co-authors are or were employees of Novonesis or PrecisionBiotics, which make the strain (Patterson et al. 2024, Sci Rep).
89 adults aged 18 to 45 with impaired sleep quality (PSQI global score 5 or higher).
The primary outcome, PSQI global score, improved in both groups with no difference at 8 weeks. The PSQI sleep quality and daytime dysfunction components improved more on the strain at week 4, and social functioning and energy were better at week 8. Actigraphy sleep measures did not differ.
Randomized, double-blind, placebo-controlled trial of 1 x 10^10 CFU a day for 8 weeks; it matches registered trial NCT04925440, sponsored by PrecisionBiotics with 168 enrolled (Seamans et al. 2026, Exp Clin Psychopharmacol).
168 adults aged 18 to 70 with mild to moderate depressive symptoms.
The primary outcome, change in Beck Depression Inventory-II score, did not differ from placebo at week 4 or week 8. At week 4, PSQI sleep scores and PHQ-9 depression scores fell more on the strain, and SF-36 vitality, mental health and social functioning were better; only vitality was still better at week 8.